Interesting read. I didn't mean to make it sound like I thought it was harmless, hence "pretty harmless" being used. Any type of smoke going into your lungs will do damage. That being said, you can purchase a vaporizer which will eliminate almost all instances of harmful smoke going into your lungs.
The posted article states that cannabis is worse for your lungs than Tobacco cigarettes. I strongly strongly disagree. Only a very small percentage of cannabis smokers will smoke more than once per day. Far less frequently than your typical cigarette smoker. Also, with cannabis, you are not inhaling the many additives that go into commercial cigarettes.
There are also studies where marijuana smoke does not have the same effect on the bronchial tubes as cigarette smoke, so heavy usage may not cause emphysema.
I'm not saying it's good for you, at all.. but I do believe that it's pretty harmless if used responsibly. Obviously, you shouldn't smoke anything daily, or worse, multiple times a day.. just as you really shouldn't drink alcohol daily either. There are people who do it, and there are people who don't.
I would be ignorant to say that it doesn't cause some bad effects if you consume so much of it. There are instances of people consuming so much cannabis that they do suffer toxic psychosis. Normally, that isn't unique to cannabis, and it's actually very rare when looking at the large picture of cannabis users..
I hope I'm not coming off as a know-it-all, cause I don't. I am simply stating my opinion. Two months ago, if this thread were around, I would be singing a different tune. I was 100% uneducated on cannabis, and then I finally decided to study it in an attempt to be more open-minded.
I think it should be legalized.. aside from people being able to smoke it freely as they please (responsibly), the plant itself is arguably just as renewable as corn, if not more. I think it would do wonders for the down economy, it can be put to use as medicine, recreation, fiber, fuel, food (said to be the "new soy"), etc. etc. etc.